People are generally aware of the most common causes of hallucinations, like schizophrenia and a really high fever. But lesser known are the more rare causes; here are six you probably haven't heard about.

Starting with an obvious one, most of us are aware caffeine can be rather disruptive. The closer your coffee break is to your bedtime, the more potential it has to disrupt your sleep. One study suggested the beverage could reduce sleep quality even when consumed up to six hours prior, encouraging a 2 p.m. cut off time.

Your dinner, on the other hand, should be sized in a way to leave you satiated without going overboard. Additionally, aim for 2 or 3 hours between your last meal and your bedtime to stave off symptoms of insomnia and nighttime heartburn.

"It’s best to avoid eating heavy meals at night," said Dr. Aris Iatridis, a sleep medicine specialist at Piedmont Healthcare. "If you’re going to have a big meal, have it in the middle of the day. You’re less likely to store the extra calories as fat because your body will have time to burn them off and you’ll be less likely to have heartburn."

In a 2016 study from Columbia University, researchers also found an association between poor sleep and higher intake of saturated fat and sugar. According to lead author Dr. Marie-Pierre St-Onge, eating more refined carbohydrates could delay the release of a hormone known as melatonin, which plays an important role in your sleep-wake cycle.

While all of the above are associated with disruptions to our slumber, the question arises as to what could actually improve our sleep quality. The same study did take note of it, revealing how participants who ate a high-fiber diet also spent more time in slow-wave sleep. This refers to the deep stage of sleep which is usually dreamless.

And the advice you often hear about drinking a glass of warm milk to sleep better? The possible basis here is that calcium (also found in foods such as leafy greens) could help you produce more melatonin. Though this may not have a significant impact on sleep, experts mentioned some individuals can see a benefit thanks to the psychological aspect.

"Our brains and physiology like routine and predictability," said Naomi Rogers, a sleep expert and professor at the University of Sydney in Australia. "[So] if someone has a routine each night of, say, watching the late news, having a warm glass of milk, brushing their teeth and getting in to bed for sleep, then the brain and our physiology recognize this behavior as part of the preparatory process for sleep and respond accordingly, making it easier to fall asleep once we are in bed."